Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc) was first reported in Brazil in 1930 on 'Maça&tild;' (AAB, Silk). Currently, the disease is present in all banana production regions of the country. Growing resistant cultivars provides the most efficient control for Fusarium wilt. In this work, seven diploid (AA) and fourteen tetraploid (AAAB) banana hybrids were evaluated in field trials for resistance to Foc in infested soil. The banana cultivars 'Maça&tild;' and 'Figue Pome Naine' (AAB, Silk) were used as susceptible controls. All diploid hybrids, namely '011601', '130404', '130406', '131801', '422306', '51A1901' and 'SH3263', showed resistance to the pathogen during both first and second crop cycle. Among the fourteen tetraploid hybrids evaluated, 'PV42-53', 'PV42-68', 'PV42-81', 'PV 42-85', 'PV42-142', 'PV42-143', 'ST42-08', 'ST12-31', 'PV03-44', 'FHIA-03' and 'SH36-40' expressed resistance to Fusarium wilt during two crop cycles, while 'PV42-129', 'PC42-01' and 'YB 42-21' behaved as susceptible. Results also showed that seven out of ten hybrids obtained from crossings in which 'M53' (AA) was used as male parent showed resistance to Foc, thus suggesting that 'M53' is a promising parent for use in banana breeding programmes aiming at developing Fusarium wilt-resistant cultivars.

The difficulty in the micropropagation of many species of Heliconaceas has been mainly due to the high frequency of endogenous contamination. Embryo culture techniques have been used to generate normal seedlings to be used as initial explants. This work aimed to develop a plant production protocol using zygotic embryos from Heliconia rostrata and H. bihai. Embryos from mature fruits were disinfested, excised and cultivated in MS medium solidified with 8% of agar, 6% of sucrose (MS + 6% S) and pH 5,8, autoclaved at 120°C for 20 minutes. The treatments were: T01: Control (MS + 6% S); T02: (MS + 6% S) + 0,25% activated charcoal; T03: (MS + 6% S) + 1,0 mg L-1 BAP; T04: (MS + 6% S) + 1,0 mg L-1 BAP + 0,25% activated charcoal; T05: (MS + 6% S) + 1,0 mg L-1 BAP + 1,0 mg L-1 GA3; T06: (MS + 6% S) + 1,0 mg L-1 BAP + 1 mg L-1 GA3 + 0,25% of activated charcoal. The embryos were maintained in dark conditions for 45 days with temperature of 27±1°C. Treatment T02 promoted the best percentage of germination (100%) for both species and T05 the lower results with 20% and 35% of germination for H. rostrata and H. bihai respective at 30 days of culture. Callus formation was observed in T05 and T06. The activated charcoal was essential to embryo germination. These seedlings were used as explants in the micropropagation assays in MS medium supplemented with these treatments: T01: MS; T02: MS + 0,25% of activated charcoal; T03: MS + 4,0 mg L-1 de BAP; T04: MS + 4,0 mg L-1 BAP + 0,25% of activated charcoal. For the multiplication stage the best medium was the control treatment with no growth regulators and no activated charcoal. A bacterial contamination appeared during subsequence subculture making the micropropagation of these species unfeasible.

Several disease resistance screening protocols for Fusarium wilt of banana (causal agent Fusarium oxysporum f. sp. cubense-Foc) under greenhouse conditions have been reported. Here, we report a standardised rapid and reliable greenhouse bioassay for this pathosystem. This is indispensable for banana phenotyping, particularly since the occurrence of tropical race 4 (TR4), which is a significant threat for the global Cavendish-based banana export industry. Using a double-pot system, hardened 3-months-old tissue-culture plants of 'Grand Naine' (AAA, Cavendish subgroup) were individually inoculated with three TR4 isolates and one race 1 isolate with known pathogenicity on 'Silk' (AAB) bananas. All TR4 isolates caused similar symptoms and no differences regarding incubation period or severity were observed. In addition, all TR4 isolates were successfully recovered from the symptomatic rhizomes on Komada medium.

Among the major constrains to banana breeding for Fusarium wilt (FW) resistance is the long period necessary for evaluations in the field and the lack of an effective method for early detection of resistant genotypes. This work aimed to establish a screening method for FW resistance under greenhouse conditions and validate its reliability by challenging cultivars with different levels of FW resistance. Two types of substrates (vermiculite and washed river sand) and three inoculums sources (conidial suspension from 1-week-old colonies grown in Potato-Dextrose-Agar-PDA, conidial suspension produced after stress of 1-week-old colonies and Foc-colonised corn meal-sand (CMS) medium) were studied by inoculating 45-dayold plantlets of 'Silk' (AAB, susceptible) in a double-tray system. Symptoms were observed in plants grown in both substrates, but highest incidence occurred in washed river sand. Low infection rates were observed using conidial suspension from PDA-grown colonies. By contrast, inocula from stressed colonies and CMS caused consistent symptom expression. Using washed river sand as substrate and inoculum from PDA-grown stressed colonies and/or Foc-colonised CMS, plantlets of the cultivars 'Tropical' (AAAB) and 'Thap Maeo' (AAB) (field intermediary resistance) were challenged. Plantlets of 'Silk' and 'Grande Naine' (AAA) were used as susceptible and resistant controls, respectively. While the incubation period in 'Silk' was 13 days after inoculation (dai), initial symptoms were only observed at 17 dai in 'Tropical' and 'Thap Maeo'. No symptoms were observed in 'Grande Naine'. The disease progress evaluated based on external symptoms and rhizome discolouration scales allowed discriminating cultivars according to resistance levels. Since experiments were repeated three times with similar results, our research suggests that the method here described could be suitable for early detection of banana genotypes resistant to Fusarium wilt.

This work aimed to evaluate the influence of naphthaleneacetic acid (NAA) and gibberellic acid (GA 3) plant regulators in in vitro etiolation and subsequent regeneration of the PE x SC-60 pineapple hybrid. Nodal segments of in vitro plants with approximately 5-7 cm height were incubated in basic MS culture medium supplemented with 0.0; 0.5 and 1.0 mg L -1of naphthaleneacetic acid (NAA) in combination with gibberellic acid (GA 3) in concentrations of 0.0; 0.5 and 1.0 mg L -1, and maintained at 27 °C ± 1°C under dark condition. Evaluations were carried out at 90 and 180 days after incubation period. The best results for length of etiolated stems were obtained with 1.0 mg L -1 of NAA. In the experiment followed by the regeneration, stems with 3 cm from the etiolation treatment, were cultivated in proliferation medium and the number of regenerated plants per treatment was evaluated at 60 days of cultivation. The treatment that promoted the best etiolation of plants also promoted the worst regeneration rates, demonstrating the residual effect of the auxin used in the previous step in the regeneration of plants of the pineapple hybrid evaluated.